Diversification and divergence of rainforest woody plants in South India and Madagascar relate to geomorphological history

Abstract

Aim Indian and Malagasy tropical rainforests share a common history that dates back to the fragmentation of Gondwana. We partitioned phylogenetic diversity across historical periods to uncover how such continental displacement led to the divergence of lineages, through vicariance and/or independent migration from other regions, influencing extant phylogenetic composition. Location Madagascar and South India (Western Ghats). Taxon Woody vascular plants (tracheophytes). Methods Using a time‐calibrated megaphylogeny, we partitioned the phylogenetic diversity of Indian and Malagasy tropical rainforest assemblages, across evolutionary periods defined based on milestone events in these regions of geological history. We decomposed the relative proportion of lineages with extant representatives in each area as well as in both areas, to quantify the common and separate biogeographical legacies in the two regions. We identified an excess or deficit of shared and unique lineages for each period and region. Results The proportion of shared lineages between Madagascar and India progressively decreased following the successive breakoff and isolation of Madagascar from the Indian‐Malagasy plate. Lineages unique to India are more numerous than expected at random in more recent time periods, whereas, lineages unique to Madagascar were significantly more present in older time periods. Main conclusions The flora of Madagascar harbours a greater number of ancient lineages than does the Western Ghats, consistent with the higher number of endemic families and genera of trees in Madagascar. More recent diversification in India could be related to the collision of India with Eurasia, which enabled subsequent biological interchanges.

Geogenomics: Toward synthesis

“…Sanín et al (2022) reveal that tectonic faulting dynamics, rather than recent mountain uplift, likely shaped phylogeographical breaks in Andean palms. Barthelemy and Munoz (2022) 2014) expounded a new core idea and identified a specific audience, it had greater impact. Yet, many papers in the special issue include components that are not encapsulated by the original definition of geogenomics (sensu Baker et al, 2014), as they do not test or constrain specific geological hypotheses, but use geological data to build predictions about biological processes (e.g.…”

“…Sanín et al (2022) reveal that tectonic faulting dynamics, rather than recent mountain uplift, likely shaped phylogeographical breaks in Andean palms. Barthelemy and Munoz (2022) evaluated processes in deeper time and examined whether the proportion of shared lineages of woody plants between India and Madagascar changed following the period of separation and isolation of Madagascar from the Indian‐Malagasy plate. Their analysis indicates that Madagascar maintained more of the ancient flora than the Western Ghats of India, likely because of expanded biotic interchange following the collision of India with Eurasia.…”